Tuning control and band switching arrangement



May 10, 1949. ABRAMS 2,469,941

TUNING CONTROL AND BAND SWITCHING ARRANGEMENT Filed March 5, 1946 2Shets-Shget 1 INVENTOR HARD/N T ABRAMJ ATTORNEY May 10, 194-9. ABRAMS2,469,941

TUNING CONTROL AND B AND SWITCHING ARRANGEMENT Filed March 5, 1946 2Sheets-Sheet 2 HARD/N TAB/MM:

v INVENTOR ATTORN EY Patented May 10, 1949 TUNING CQNTROL AND BANDSWITCHING ARRANGEMENT Hardin 'll. Abrams, Cedar Rapids, Iowa, assignorto Qollins Radio Company, Cedar Rapids, Iowa, a corporation of IowaApplication March 5, 1946, Serial No. 652,156

2 Claims.

This invention relates to multiple tuned circuits such for example asare used in radio sets, and more particularly to a multi-frequency bandtuning arrangement capable of continuous coverage of a wide range offrequencies.

Various arrangements have been devised heretofore for enabling wavecoupling circuits to be tuned over a wide frequency range. When therequired frequency range coverage is too large to be accomplished bysingle adjustable components Whether capacitative or inductive, resorthas been had to multi-contact switches for switching from one tuningcombination to another tuning combination. Among the disadvantages ofsuch conventional band-changing arrangements are th following. A changein contact resistance may take place at the switch contacts whichbecause of their inclusion in the tuned circuit, causes a change in thedesired resonance of the tuning circuit. When the adjustable condenseris designed for tuning over a wide frequency range and has optimumtuning effect within a particular frequency band, it causes a crowdingof the frequencies when adjusted to cover a higher frequency band.Furthermore, the adjustable capacitor used for tuning the circuit over avery wide range may be too large for maximum efficiency of operation.

Accordingly. it is a principal object of this invention to provide atuning control system for use with radio apparatus and the like, whichsystem provides the correct inductance-to-capacity ratio required forthe tunin over each frequency band of a series of such bands.

It is also an obiect of this invention. to provide a tuning controlsystem suitable for use over a wide range of freouencies and capable ofcovering each successive frequency band of a series; and whereinconnection is automatically made to the correct frequency-determinincombination in a series of such combinations while employing a minimumnumber of switching contacts.

It is another object of this invention to provide a tuning controlsystem for multi-band operation wherein the band spread on each band canbe given any desired magnitude.

It is a further object of this invention to pro vide a tunin controlsystem employing successive frequency bands covering a wide frequencyrange wherein. the functions of tuning and band switching areaccomplished by a single adjusting member such a tuning dial.

A feature of the invention relates to an improved dual section tuningsystem each section 2 havin separate inductance coils for operation overpredetermined frequency bands and separate adjustable condenser platesfor operation over each of said bands.

Another feature relates to a compact and mechanically symmetrical unitfor controlling the tuning of a radio set or the like over a successionof frequency bands.

A further feature relates to a unitary multiband tuning and band-changeunit, comprising a rotatable drum carrying a plurality of separate setsof condenser plates arranged around the periphery thereof, and carryingon its interior in separate shielded compartments a series of inductancecoils which cooperate with corresponding condenser plates.

A still further feature relates to a novel compact unit for tuning adevice such as a multiband radio receiver, over a series of frequencybands, the device having sets of condenser stator plates and sets ofcondenser rotor plates. The rotor plates are peripherally spaced arounda. hollow drum-like member havin a single ad-. justing shaft. Located onthe interior of this drum-like member in separate shielded compartmentsare the respective tuning inductances for the various frequency bands. Acommutator segment arrangement is carried by the drumlike member so thatmerely by turning said member the proper combination of rotor and statorcondenser plates are chosen as well as the proper tuning inductance tocooperate therewith.

A further feature relates to the novel multi-. band sunerheterodyneradio receiver.

A still further feature relates to the novel organization, arrangementand interconnection of parts which cooperat to produce an improvedmulti-band tuned circuit system for operation over a wide frequencyrange.

Other features and advantages not particularly enumerated. will beapparent after a consideration of the following detailed descriptionsand the, appended claims. 1

In the drawing,

Fig. 1 is a schematic wiring and block diagram showing a superheterodyneradio receiver embodying the inventive concept.

Fig. 2. is a front view of one preferred tuning control according to theinvention.

Fig. 3 isa side elevation view of Fig. 2.

Merely for purposes of explanation, the in: vention will be describedand ilustrated as applied to the tuning of the frequency conversionosclllator stage and the mixer stage of a conventional superheterodyneradio receiver. It will be underfl denserairotor platesrtllf'fs I.

stood that the inventive concept is applicable to any other plurality ofunits which are required to be tuned in tracked relation by adjustablecapacitors.

Referring more particularly to Fig. 1, the designations I0, II,represent respectively the tuning sections 'vwhicluare tadaptedrrespectively to tune the-mixer I2 and-"the local'heterodyne oscillator I3. The mixer l2 may have its input supplied from any suitable radiofrequency amplifier I4 connected to a receiving-antenna :i 5. The outputof mixer I2 is applied to the intermediate frequency amplifier I6 whichin turn is connected to a suitable detectorljlrand a-suitable audiofrequency amplifier I8;"which"-is-connected to a suitable translator orloud speaker I 9. Merely for illustrative purposes, thereceilieriisishown as having four separate tuning bands, althoughagreater or less number may be used. The tuning and band-change sectionII] comprises four par- 34335; 36:31. Likewise, thecommutator 38comprises a stationary brush*39 and-its"cooperatingrotatablecommutatorsegments 4D, 4!; 42 and All the commutator segmentsaremounted around Zi'COm-IIIOH 'shaft-whichis:adapted to-rotate the saidsegments as a unit. The arrangement of the segments 'is such that duringone'* quadrant of revolution, contact isma'deb'etween brush22 andsegment'2-3 between brdshfZI, and segment, at; between brush 33. and.segment 34 and. between brush .39and segment '10. J As the commutatorsegments are rotated,1it willbeclearthat the remaining segments ;are'likewise-connected in .circui ts in sets .of four bytheir respectivebrushes. Permanently connected-totheSegments 23 audit, is an"inductance,.coiI"'44 "and." the "terminals of this inductancecoil areconnectedrespectivelyto condenser rotor plates 45,"'4B.""WhilefFig.lshows the plates '45 andIIB as'consistingbfasingle element, it will beunderstood thatthisismerely schematic andthateach element'will" consistof' a. bank of spacedcondenser rotor plates as will be described inconnection with Figs; '2 and'.'3.

* Likewisa permanently' connected "to. the segments 34 and 40 is thein'ductance COil'lW which hasits terminals" connectedto condenser rotorplates 48;49. In'aJsnnilar-inanner, segments H and "29 areconnected'toiiiductance'coil 58, the terminals of which are connectedto; the condenser rotor plates .51, 52. Likewise, commutator ments35and4 I are connected'permanently to the inductance "coil"'53' which" has"its terminals connected to the condenserrotor plates-54;155. Segments"and .are permanently; connected to inductance coil "56"whose terminalsare connect-ed to condenser rotor 'platest"'51;" 58. Segments and 42 arepermanently connected to inductance coil?'59'whosefterminals-i'areicon-nected tocon- Similarly; ithe segmentsz 6 and}tarepermanently connected to inductancecbil "B2"whose"te"r1ninals areconnected-to -sive quadrants, each successive set of rotor plates isbrought into electrostatic mesh with the common stator plates 68-69.Likewise, the various sets of rotor plates in unit I I are provided witha common set of stator plates I0, I I, so that as the common shaft forthe commutators is rotated throughsuccessive quadrants, the rotor platesof unit I I are successively brought into electrostatic mesh with thestator plates It and l I. It will be clear" from the: foregoingtherefore; that 3 since "all the rotor plates of both: units and. allithe commutatorsegments-of both tunits'slll and II are controlled by thesame shafui'the' mere turning of this shaft automaticallybringsz'theproperr-set oi condenser-rotor plates :into mesh-with thecoopcrating stator plates and-ati-the same tirne automatically connectsin circuit the proper one of the tuning'inductances in each of theunitsIii, -1'I I. It will be understood that in accordance with conventionalsuperheterodyne practice; the values of the inductance coils :fortheoscillator unit -I i, and the values of the :condenserunitsare chosen soas to produce a-constant frequency difference with respect to thetuning-of the mixer unit it. In other words, regardless of which band-isselected'for use by rotating'the common shaft, which is'represented bythe dotted line in- Fig. -1,*tl1ere will be produced at all settings thesame tuned frequency difierence between-units I e and i 1.

One preferred structural embodiment of the units It, II,-is illustratedillFigSl' z-and 3; wherein parts corresponding functionally tothose ofFig.

I bear the same designation numerals.

The dru n E2 of metal orother suitable material'has its end plates '53;Myfastened-toshaft"l5 passing centrally through thedrumand mountedforrotation in suitable-bearing brackets 16, ll. Shaft '55 passes throughmember 'Ieand has at its end a suitable turning knobor dial l8. Thegroupof rotor plates 45, 5 I; 51,63, are mounted acircumferential'rowonsuitable insulated lorack ts it carried bythe drum so that, all the lingplates of each successive group'are in circumferential alignment, "butwith each group spaced apart from the succeeding group 50 that eachgroupof plates occupies-approximately one quadrant of the-drum periphery.Likewise, the rotor plates -46; 52, 5B and 64 are mounted in acircumferential row around-the periphery of the drum but are axiallydisplaced from the correspondingplatesfi, 5!;51 andg53. The rotor platesof unit II are mounted in a'similar manner around the periphery; of"drum "12. Extending between the plates I6 and TI are'four tie-membersi9, 89, 8!, 82. Each ofthese'tie members consists ofiourmetal'rods83;184, 85,86, which are ri idly joined together byintervening insulating members 81, 88, 89. Supported on the sections 35of each of'the tie members I9, 8 0, 85, 32, are ,the stator, condensergroups I58, .69. Likewise supported on the sections,-B'1,,0f.,1tlrese.tie members arethe stator ilqllfilflllfier ggroups.10, ,H. The various sets ,Of statol,fg;lzl itesicare mountedso as to beinterleaved 'electrostatically'with the various rotor plates as the drum72 is rotated. The interior of drum 72 is divided into four cylindricalquadrants by means of the intersecting longitudinal partitions 99, 9!.Likewise, the interior of the drum may be divided into two halves by acentral transverse wall 92. By this arrangement, the interior of thedrum is divided into eight separate compartments. In each of thesecompartments suitably mounted the corresponding one of the eightinductance coils M, 50, 56, 62, 41, 53, 59, 65. As indicatedschematically in Fig. 1, one terminal of inductance id is connected byan insulated wire which passes through a suitable small opening in druml2 and is electrically connected to the plates t5, the opposite terminalof the coil M is likewise connected by a suitable insulated wire to thelongitudinally adjacent set of rotor plates 49. Likewise the remainingcoils tit, 58 and 62 are connected to respective sets of rotor plates.Thus coil 58 is connected to plates 5!, 52; coil 58 is connected toplates 57, '58; and coil 82 is connected to plates 83, 9t. Suitablyfastened to the right-hand end of the drum 52 so as to be insulatedtherefrom, are the commutator segments to 28, and 28 to 31. Likewise,insulatingly fastened to the left-hand end of the drum periphery are thecommutator segments 84' to 37 and 49 to 58. Insulatingly mounted in thememher 59 are the stationary brushes 22 and 21. Likewise, insulatinglymounted in the member ii are the stationary brushes 33 and 39. Each ofthe commutator segments occupies approximately one quadrant of the drumperiphery and the connections from the various segments to therespective inductance coils and the respective sets of rotor plates areindicated in Fig. 1.

As shown more clearly in Fig. 2, the stator plates have curvedperipheries corresponding to the curvature of the drum l2 and aremounted in spaced relation to the drum periphery.

It will be understood that the various condenser plates may be given anyplanar configuration in accordance with the desired law of capacityvariation. Thus, if a linear relation is desired between incrementalcapacity change with incremental movement, the rotor plates can bedesigned as follows.

R=the peripheral radius of drum I2 Co=the stray capacity fo=the lowestfrequency to be covered f=the highest frequency to be covered 0=theangular displacement of the rotor plate =the arc through which the rotorplate travels from zero to maximum electrostatic mesh Kc=dielectricconstant multiplied by the number of rotor plates used, and

=the distance from the axis of rotation to the outer edge of the rotorplate.

While there has been here described one preferred embodiment, it isunderstood that various changes and modifications may be made thereinwithout departing from the scope of the invention.

What is claimed is:

1. A tuning control and band-change arrangement for radio sets and thelike, comprising a rotatable drum of conductive material, a firstinductance coil carried interiorly of said drum and rotatable as a unittherewith, a first condenser rotor plate insulatingly mounted on theexternal periphery of said drum and electrically connected to oneterminal of said first inductance, a second condenser rotor plateinsulatingly mounted on the external periphery of said drum andelectrically connected to another terminal of said first inductance,said first and second plates being of similar segmental shape and ofco-extensive circumferential length around the periphery of said drumbut being displaced from each other longitudinally of said drum, asecond inductance coil carried interiorly of said drum and rotatable asa unit therewith, a third condenser rotor plate insulatingly mounted onthe external periphery of said drum and electrically connected to oneterminal of said second inductance, a fourth condenser rotor plateinsulatingly mounted on the external periphery of said drum andelectrically connected to another terminal of said second inductance,said third and fourth plates being of similar segmental shape andcircumferential extension around the periphery of the drum with thethird plate in circumferential alignment with the first plate and thefourth plate in circumferential alignment with the second plate,respective stator condenser plates for said rotor plates fixedly mountedadjacent said drum, commutator means carried by said drum for connectingeach of said inductances and their respective electrically connectedrotor plates to a common utilisation circuit, and a single control shaftfor rotating said commutator and said drum to effect continuousband-change and tuning within each band.

2. A tuning control and band change arrangement according to claim 1, inwhich said drum is divided by a conductive wall into longitudinalcompartments and each longitudinal compartment is divided by respectiveconductive walls into respective radial compartments, and within eachradial compartment is mounted one of said inductance coils.

HARDIN T. ABRAMS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,687,500 Langley Oct. 16, 19281,988,444 Carpenter Jan. 22, 1935 2,039,885 Chunn May 5, 1936 2,078,909Gunther Apr. 27, 1937 2,290,875 Griebach July 28, 1942 2,385,131Garthwaite Sept. 18, 1945

